Preheat oven to 350

Line cookie sheet with parchment paper.

In a small bowl mix together cocoa, baking soda, flour and salt.

In a medium bowl beat together butter, sugar, eggs and vanilla until fluffy.

Gradually add in your cocoa mixture and beat well.

Bake for 10-12 minutes. Allow to cool.

Combine the egg whites and vanilla and beat until bubbly.

Add powdered sugar gradually and mix until all sugar is incorporated.

Beat on high until mixture forms stiff, glossy peaks.

Transfer to pastry bag and pipe pattern on cookies.